Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
A fixing device, which is internally included in an electrophotographic or electrostatic recording type image forming apparatus, causes a sheet on which a toner image is formed by a previous process to pass and be sandwiched between two rollers (hereinafter referred to as a fixing nip area), a heating roller and a pressure roller. Thus, the fixing device applies pressure to and heats this sheet to fix the toner image. When a head of the sheet contacts a pressure roller before the head of the sheet reaches a fixing nip area, the sheet is easily caught in the pressure roller by an elastic layer of the pressure roller in the fixing device described above. This may generate a wrinkle on the sheet.
It is known that guiding the head of the sheet conveyed by a conveyance guide to a position close to the heating roller at an upstream side of the fixing nip area can prevent such wrinkle generation. A fixing device that prevents the wrinkle generation when curling a comparatively light and inelastic sheet has been disclosed. Additionally, the fixing device reduces a generation of a toner image disturbance due to a collision between a distal end of the sheet and a guiding portion when using a thick sheet.